The invention is based on a plate-shaped, optical storage medium and reading device.
A plate-shaped, optical storage medium has been disclosed by German Patent Document 4311683. These storage mediums which are generally referred to as CDs (compact disc) contain binary data which are stored serially in a sequence of heights and depths along a spiral track. The CD is embodied as a round disc upon which the spiral track goes from the inside to the outside. For scanning, the disc is set into a circular rotational motion, wherein in order to achieve a constant data flow density, the rotation speed decreases during a scan from the inside toward the outside.
A CD reading device has been disclosed, for example, by German Disclosure Document 4225727. In order to scan the CD, the laser diode, whose light is reflected on the surface of the CD, is moved radially over the CD which is rotating at different speeds.
EP-A-0 666 565 has disclosed a reading device for reading an optical card, which includes an optical reading head with a laser diode and optical lenses for focusing the laser beam. The optical reading head also includes an optical sensor for detecting the reflected laser beam. The optical card rests on a spacer ring, which assures a certain distance between the objective lenses of a rotary plate and the optical card. The rotary plate with the objective lenses of the scanning head is set into rotation in order to optically scan the optical card.
U.S. Pat. No. 4,656,346 has disclosed an optical system for reading an optical card in credit card format. The optical system includes a laser light source, which emits a laser beam that passes through focusing optics. Furthermore, there are known detectors which detect the laser beam that is held by movable retention device. The laser beams follow the tracks of the optical storage card by virtue of the fact that the retention device is moved in the longitudinal direction of the card in relation to the laser beams.
The plate-shaped, optical storage medium according to the invention has the advantage over the prior art that it has a small, convenient format, which has the shape and size of a standard card according to ISO 7810. The optical storage medium according to the invention provides a small exchangeable storage medium which can be inexpensively manufactured and is not sensitive to environmental influences. Therefore primarily, it can be used very easily in mobile devices, for example in a motor vehicle. It is particularly advantageous that despite the small dimensions of the storage medium, a large quantity of data can be stored.
An advantageous improvement and update of the storage medium is possible by means of the measures taken in the dependent claims. The storage volume can be advantageously doubled by using both sides of the storage medium.
The data are written along tracks which are disposed either parallel or perpendicular to the longitudinal axis of the card. As a result, the data can be read without the card according to the invention having to be set into rotation in the reading device as was previously the case with conventional storage plates.
The reading device according to the invention for reading the plate-shaped, optical storage medium in the standard card format advantageously has a suitable opening for receiving the optical storage medium as well as at least one laser diode for reading the data. The reading device does not require a motor that sets the optical storage medium into a rotating motion and does not require a movable scanning head which moves really over the surface of the storage medium. The reading device consequently has significantly fewer components since movements of the storage medium itself are eliminated.
The reading device advantageously has at least one laser diode, whose light follows the track of the storage medium. It is advantageous that for a very rapid reading potential, a laser array is installed in which a number of laser diodes simultaneously emit light and can detect data by using the interference process.
Advantageously, the beam of the laser diode follows the track of the storage medium by means of an optical device wherein this device can be a movable mirror or an electrooptical component.
In another embodiment of the reading device, a mechanical movement of the scanning head in the plane over the storage plate is advantageous in order to prevent a large deflection angle of the beam away from the perpendicular to the storage surface.